[Bug c++/53039] New: [C++11]including <functional> breaks std::is_convertible with template-pack expansion

[Bug c++/53039] New: [C++11]including <functional> breaks std::is_convertible with template-pack expansion

[mitchnull+gcc at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53039

             Bug #: 53039
           Summary: [C++11]including <functional> breaks
                    std::is_convertible with template-pack expansion
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: mitchnull+gcc@gmail.com


Created attachment 27185
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27185
test code

#include <functional> in the following code causes compile failure. Without the
include, it compiles fine:

#include <type_traits>
#include <functional> // without this include, it compiles

template <bool... Bs_>
struct Bools {
    static const bool value = true;
};

template <typename... Ts_>
struct Types {
    template <typename... Us,
             typename std::enable_if<
                 Bools<std::is_convertible<Us, Ts_>::value...>::value,
                 bool>::type = false>
    int foo(Us&&...) {
        return sizeof...(Us);
    }
};

int main() {
    Types<int, int> t;
    return t.foo(1, 1);
}


Output:

$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-unknown-linux-gnu/4.7.0/lto-wrapper 
Target: x86_64-unknown-linux-gnu
Configured with: /build/src/gcc-4.7-20120324/configure --prefix=/usr
--libdir=/usr/lib --libexecdir=/usr/lib --mandir=/usr/share/man
--infodir=/usr/share/info --with-bugurl=https://bugs.archlinux.org/
--enable-languages=c,c++,ada,fortran,go,lto,objc,obj-c++ --enable-shared
--enable-threads=posix --with-system-zlib --enable-__cxa_atexit
--disable-libunwind-exceptions --enable-clocale=gnu --disable-libstdcxx-pch
--enable-libstdcxx-time --enable-gnu-unique-object --enable-linker-build-id
--with-ppl --enable-cloog-backend=isl --enable-lto --enable-gold
--enable-ld=default --enable-plugin --with-plugin-ld=ld.gold
--with-linker-hash-style=gnu --disable-multilib --disable-libssp
--disable-build-with-cxx --disable-build-poststage1-with-cxx
--enable-checking=release
Thread model: posix
gcc version 4.8.0 20120407 (experimental) [trunk revision 186212] (Debian
20120407-1)

$ /usr/lib/gcc-snapshot/bin/g++ -std=c++11 functional_bug.cpp
functional_bug.cpp: In instantiation of 'struct Types<int, int>':
functional_bug.cpp:21:21:   required from here
functional_bug.cpp:15:9: error: wrong number of template arguments (3, should
be 2)
In file included from functional_bug.cpp:1:0:
/usr/lib/gcc-snapshot/lib/gcc/i486-linux-gnu/4.8.0/../../../../include/c++/4.8.0/type_traits:1264:12:
error: provided for 'template<class _From, class _To> struct
std::is_convertible'
functional_bug.cpp: In function 'int main()':
functional_bug.cpp:22:14: error: 'struct Types<int, int>' has no member named
'foo'

[Bug c++/53039] [C++11]including <functional> breaks std::is_convertible with template-pack expansion

[mitchnull+gcc at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53039

--- Comment #2 from Radics Péter <mitchnull+gcc at gmail dot com> 2012-04-19 08:00:00 UTC ---
Created attachment 27187
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27187
4.7.0 output

test run on arch linux

[Bug c++/53039] [C++11]including <functional> breaks std::is_convertible with template-pack expansion

[mitchnull+gcc at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53039

--- Comment #1 from Radics Péter <mitchnull+gcc at gmail dot com> 2012-04-19 07:59:06 UTC ---
Created attachment 27186
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27186
4.8.0 output

test run by sam of #c++ on freenode

[Bug c++/53039] [C++11]including <functional> breaks std::is_convertible with template-pack expansion

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53039

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2012-04-19
     Ever Confirmed|0                           |1

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-04-19 08:41:54 UTC ---
Very strange. Confirmed.

[Bug c++/53039] [4.7/4.8 Regression] including <functional> breaks std::is_convertible with template-pack expansion

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53039

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|mitchnull+gcc at gmail dot  |hjl.tools at gmail dot com
                   |com                         |
            Summary|[C++11]including            |[4.7/4.8 Regression]
                   |<functional> breaks         |including <functional>
                   |std::is_convertible with    |breaks std::is_convertible
                   |template-pack expansion     |with template-pack
                   |                            |expansion

--- Comment #4 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-04-19 10:45:53 UTC ---
Looks like a regression. I wonder if isn't some sort of weird side-effect of
the fix for PR48322: we should at least compare pre and post Rev 181547. Then
do a binary search. 

HJ, can you help with the search? (mind the -std=c++11)

[Bug c++/53039] [4.7/4.8 Regression] including <functional> breaks std::is_convertible with template-pack expansion

[hjl.tools at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53039

--- Comment #5 from H.J. Lu <hjl.tools at gmail dot com> 2012-04-19 14:49:32 UTC ---
(In reply to comment #4)
> HJ, can you help with the search? (mind the -std=c++11)

My regression hunt machine is down. It will take a while to
get it back.

[Bug c++/53039] [4.7/4.8 Regression] including <functional> breaks std::is_convertible with template-pack expansion

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53039

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jason at gcc dot gnu.org

--- Comment #6 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-04-19 15:58:17 UTC ---
Too bad, didn't know that. Then I'll do something myself ASAP.

In the meanwhile, at the risk of appearing a bit boring, let me add Jason in CC
for this one too, the issue seems quite "interesting" ;)

[Bug c++/53039] [4.7/4.8 Regression] including <functional> breaks std::is_convertible with template-pack expansion

[daniel.kruegler at googlemail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53039

--- Comment #7 from Daniel Krügler <daniel.kruegler at googlemail dot com> 2012-04-20 06:48:39 UTC ---
I'm pretty sure that this is not related with <functional>, but instead with
some interaction between the <tuple> header and std::is_convertible. The
following variant still demonstrates the problem (I deliberately changed some
of the original names used in the code to be sure that they are not cause of
the problem):

#include <tuple>

template<bool, class T>
struct enable_if
{
  typedef T type;
};

template <bool...>
struct Bs
{
  static const bool value = true;
};

template <typename... Ts>
struct AType {
  template <typename... Us,
            typename enable_if<
               Bs<std::is_convertible<Us, Ts>::value...>::value,
               bool>::type = false
  >
  int foo(Us&&...)
  {
    return sizeof...(Us);
  }
};

int main() {
  AType<int, int> t;
  return t.foo(1, 1);
}

(You can also add <type_traits>, but it is already added via <tuple>). If we
now add upfront

template <class, class>
struct is_convertible
{
  static const bool value = true;
};

and replace the usage of std::is_convertible by is_convertible, the error does
no longer occur.

[Bug c++/53039] [4.7/4.8 Regression] including <functional> breaks std::is_convertible with template-pack expansion

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53039

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|hjl.tools at gmail dot com  |

--- Comment #8 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-04-20 09:06:30 UTC ---
Thanks Daniel. If you feel like helping even more here, I would suggest having
a look to the output of g++ -E and check that we aren't goofing something in
terms of include guards, double inclusions, these kinds of stupid errors which
often lean to very poor diagnostics, unfortunately. That done, I can only
imagine a front-end issue.

[Bug c++/53039] [4.7/4.8 Regression] including <functional> breaks std::is_convertible with template-pack expansion

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53039

--- Comment #9 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-04-20 10:27:11 UTC ---
Eh, this is *not* a library issue:

#include <type_traits>

#if 1

template<typename... _Elements>
  class tuple
    {
      template<typename... _UElements, typename = typename
           std::enable_if<std::__and_<std::is_convertible<_UElements,
           _Elements>...>::value>::type>
        tuple(_UElements&&...);
    };

#else

template<typename _Elements>
  class tuple1
    {
      template<typename _UElements, typename = typename
           std::enable_if<std::__and_<std::is_convertible<_UElements,
           _Elements>>::value>::type>
        tuple1(_UElements&&);
    };

#endif

template <bool...>
struct Bs
{
  static const bool value = true;
};

template <typename... Ts>
struct AType {
  template <typename... Us,
            typename std::enable_if<
               Bs<std::is_convertible<Us, Ts>::value...>::value,
               bool>::type = false
  >
  int foo(Us&&...)
  {
    return sizeof...(Us);
  }
};

int main() {
  AType<int, int> t;
  return t.foo(1, 1);
}

[Bug c++/53039] [4.7/4.8 Regression] including <functional> breaks std::is_convertible with template-pack expansion

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53039

--- Comment #10 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-04-20 12:37:33 UTC ---
So, the below is my final pure C++ testcase: if 1 is changed to 0 the code
compiles; likewise if 1 and 0 are swapped. Thus, it seems there is something
wrong in global front-end data structures:

template <class, class>
struct is_convertible
{
  static const bool value = true;
};

template<bool, class T>
struct enable_if
{
  typedef T type;
};

template <bool...>
struct Xs
{
  static const bool value = true;
};

#if 1
template<typename... Ts>
  class BType
    {
      template <typename... Us,
        typename enable_if<
               Xs<is_convertible<Us, Ts>::value...>::value,
               bool>::type = false>
        void fooX(Us&&...);
    };
#endif

template <typename... Ts>
  struct AType
    {
      template <typename... Us,
    typename enable_if<
               Xs<is_convertible<Us, Ts>::value...>::value,
               bool>::type = false>
        void foo(Us&&...);
    };

#if 0
template<typename... Ts>
  class CType
    {
      template <typename... Us,
        typename enable_if<
               Xs<is_convertible<Us, Ts>::value...>::value,
               bool>::type = false>
        void fooX(Us&&...);
    };
#endif

int main()
{
  AType<int, int> t;
  t.foo(1, 1);
}

[Bug c++/53039] [4.7/4.8 Regression] including <functional> breaks std::is_convertible with template-pack expansion

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53039

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.7.1

[Bug c++/53039] [4.7/4.8 Regression] including <functional> breaks std::is_convertible with template-pack expansion

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53039

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2

[Bug c++/53039] [4.7/4.8 Regression] including <functional> breaks std::is_convertible with template-pack expansion

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53039

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |dodji at gcc dot gnu.org,
                   |                            |jakub at gcc dot gnu.org

--- Comment #11 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-05-02 11:46:24 UTC ---
The #c10 testcase started failing with
http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=170341
with:
pr53039.C: In function 'int main()':
pr53039.C:56:5: error: 'struct AType<int, int>' has no member named 'foo'

[Bug c++/53039] [4.7/4.8 Regression] including <functional> breaks std::is_convertible with template-pack expansion

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53039

--- Comment #12 from Jason Merrill <jason at gcc dot gnu.org> 2012-06-11 05:59:25 UTC ---
(In reply to comment #11)
> The #c10 testcase started failing with
> http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=170341

Right.  Using DECL_NAME to compare parameter packs doesn't work if one
parameter pack can be replaced by another in substitution.  In both BType and
AType, we have

               Xs<is_convertible<Us, Ts>::value...>::value,

and the appearance in AType ends up replaced by the version from BType, so when
we compare the Us to the AType parameter, they don't match.  Clearly they
should match.  I think comparing the decls was my idea, sorry.

[Bug c++/53039] [4.7/4.8 Regression] including <functional> breaks std::is_convertible with template-pack expansion

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53039

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.7.1                       |4.7.2

--- Comment #13 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-06-14 08:47:08 UTC ---
GCC 4.7.1 is being released, adjusting target milestone.

[Bug c++/53039] [4.7/4.8 Regression] including <functional> breaks std::is_convertible with template-pack expansion

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53039

--- Comment #14 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-06-14 10:03:07 UTC ---
Thus, is it possible that a different approach at fixing PR46394, among those
already envisaged, could work for this one?

Maybe Dodji can look again into it? He has already analyzed in detail the
involved code, AFAICS.

[Bug c++/53039] [4.7/4.8 Regression] including <functional> breaks std::is_convertible with template-pack expansion

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53039

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
         AssignedTo|unassigned at gcc dot       |jason at gcc dot gnu.org
                   |gnu.org                     |

[Bug c++/53039] [4.7/4.8 Regression] including <functional> breaks std::is_convertible with template-pack expansion

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53039

--- Comment #15 from Jason Merrill <jason at gcc dot gnu.org> 2012-07-05 19:39:07 UTC ---
Author: jason
Date: Thu Jul  5 19:39:01 2012
New Revision: 189298

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=189298
Log:
    PR c++/50852
    PR c++/53039
    * tree.c (strip_typedefs_expr): New.
    * cp-tree.h: Declare it.
    * pt.c (convert_template_argument, unify): Use it.
    * parser.c (cp_parser_template_declaration_after_export): Don't call
    fixup_template_parms.

Added:
    trunk/gcc/testsuite/g++.dg/cpp0x/variadic133.C
    trunk/gcc/testsuite/g++.dg/template/typedef39.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/cp-tree.h
    trunk/gcc/cp/parser.c
    trunk/gcc/cp/pt.c
    trunk/gcc/cp/tree.c
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/g++.dg/template/param1.C

[Bug c++/53039] [4.7/4.8 Regression] including <functional> breaks std::is_convertible with template-pack expansion

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53039

--- Comment #16 from Jason Merrill <jason at gcc dot gnu.org> 2012-07-05 21:24:43 UTC ---
Author: jason
Date: Thu Jul  5 21:24:33 2012
New Revision: 189305

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=189305
Log:
    PR c++/53039
    * pt.c (arg_from_parm_pack_p): Go back to using same_type_p or
    cp_tree_equal.

Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/pt.c

[Bug c++/53039] [4.7 Regression] including <functional> breaks std::is_convertible with template-pack expansion

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53039

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[4.7/4.8 Regression]        |[4.7 Regression] including
                   |including <functional>      |<functional> breaks
                   |breaks std::is_convertible  |std::is_convertible with
                   |with template-pack          |template-pack expansion
                   |expansion                   |

--- Comment #17 from Jason Merrill <jason at gcc dot gnu.org> 2012-07-06 01:34:09 UTC ---
Fixed on trunk.

[Bug c++/53039] [4.7 Regression] including <functional> breaks std::is_convertible with template-pack expansion

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53039

--- Comment #18 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-09-13 10:31:18 UTC ---
Jason, are we still considering backporting something? It would be great - I
find the issue pretty annoying - but it's your call.

[Bug c++/53039] [4.7 Regression] including <functional> breaks std::is_convertible with template-pack expansion

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53039

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.7.2                       |4.7.3

--- Comment #19 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-09-20 10:21:00 UTC ---
GCC 4.7.2 has been released.

[Bug c++/53039] [4.7 Regression] including <functional> breaks std::is_convertible with template-pack expansion

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53039

--- Comment #20 from Jason Merrill <jason at gcc dot gnu.org> 2012-11-29 20:16:57 UTC ---
Author: jason
Date: Thu Nov 29 20:16:46 2012
New Revision: 193955

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=193955
Log:
    PR c++/50852
    PR c++/53039
    * tree.c (strip_typedefs_expr): New.
    * cp-tree.h: Declare it.
    * pt.c (convert_template_argument, unify): Use it.
    * parser.c (cp_parser_template_declaration_after_export): Don't call
    fixup_template_parms.

    * cp-tree.h (TEMPLATE_PARM_NUM_SIBLINGS): Remove.
    (struct template_parm_index_s): Remove num_siblings.
    * pt.c (fixup_template_parms, fixup_template_parm_index): Remove.
    (fixup_template_type_parm_type): Remove.
    (build_template_parm_index): Remove num_siblings parm.
    (process_template_parm): Likewise.
    * parser.c (cp_parser_template_parameter_list): Adjust.
    * tree.c (cp_tree_equal): Don't compare num_siblings.
    * typeck.c (comp_template_parms_position): Likewise.

    * pt.c (arg_from_parm_pack_p): Go back to using same_type_p or
    cp_tree_equal.

Added:
    branches/gcc-4_7-branch/gcc/testsuite/g++.dg/cpp0x/alias-decl-20.C
    branches/gcc-4_7-branch/gcc/testsuite/g++.dg/cpp0x/variadic133.C
    branches/gcc-4_7-branch/gcc/testsuite/g++.dg/template/typedef39.C
Modified:
    branches/gcc-4_7-branch/gcc/cp/ChangeLog
    branches/gcc-4_7-branch/gcc/cp/cp-tree.h
    branches/gcc-4_7-branch/gcc/cp/parser.c
    branches/gcc-4_7-branch/gcc/cp/pt.c
    branches/gcc-4_7-branch/gcc/cp/tree.c
    branches/gcc-4_7-branch/gcc/cp/typeck.c
    branches/gcc-4_7-branch/gcc/testsuite/ChangeLog
    branches/gcc-4_7-branch/gcc/testsuite/g++.dg/template/param1.C

[Bug c++/53039] [4.7 Regression] including <functional> breaks std::is_convertible with template-pack expansion

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53039

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED

--- Comment #21 from Jason Merrill <jason at gcc dot gnu.org> 2012-11-29 20:57:15 UTC ---
Fixed for 4.7.3.